Blowdown Fuel Cost

Combines blowdown heat loss, boiler efficiency, and fuel unit cost into the hourly fuel penalty of operating at a given blowdown rate.

$$\text{Fuel cost (\$/hr)}=\frac{BD\times C_p\times \Delta T}{\text{Boiler Efficiency}\times 1,000,000}\times \text{Fuel cost (\$/MMBTU)}$$

Variables

Symbol	Meaning	Unit
BD	Blowdown rate	lb/hr
$C_p$	Specific heat of water (approximately 1.0)	BTU/lb·°F
$\Delta T$	Blowdown temperature minus makeup temperature	°F
Boiler Efficiency	Fraction of fuel energy delivered as useful heat	dimensionless
1{,}000{,}000	Conversion factor, BTU per MMBTU	BTU/MMBTU
Fuel cost	Unit cost of fuel	$/MMBTU

Worked example

152,000 BTU/hr heat loss / 0.8 = 190,000 BTU/hr fuel input. (190,000 / 1,000,000) × $10=$1.90/hr. Over 8,760 hr/yr that is $1.90\times 8,760=$16,644/yr fuel penalty.

---

Part of The Blueprint of Water